This invention arose out of a further development associated with the centrifugal media mill disclosed in U.S. Pat. No. 4,244,531. The centrifugal media mill includes a vessel having a wall thereon with an opening therein through which a shaft extends. In this particular embodiment, the vessel rotates with respect to a stationary shaft. Further, the vessel is provided with an inlet port and an outlet port facilitating the flow of a liquid substance through the vessel. The vessel is filled with a particulate grinding media and, as the vessel rotates, the media acts upon the liquid substance to process same in a desirable manner. The grinding media has the ability to work its way toward the seal between the shaft and the wall of the vessel and can attack and damage the seal thereat. Further, liquid substance becomes entrapped within this region. Thus, when the processing operation is completed, and it becomes necessary to flush the remaining liquid substance from the vessel by passing a solvent through the vessel, the solvent, in many instances, will not reach the gap between the shaft and the vessel wall and the remaining and entrapped liquid substance will not be removed by the solvent. Thus, a new liquid substance entering the vessel will be contaminated by the previous substance that had passed through the mill.
Thus, a need has arisen to prevent the grinding media from attacking the seal components as well as preventing the liquid substance being processed within the mill from entering a gap between a shaft and a wall of the vessel.
It is to be recognized that while this invention arose out of a need in a particular environment, it is to be understood that the specific environs of the invention is not to limit the scope of the invention in any respect.
Accordingly, it is an object of this invention to provide a mechanical seal having a pair of seal members, one being fixed with respect to a wall and the other being fixed with respect to a shaft, which seal members are in mutually contacting relation to each other, the seal member fixed with respect to the wall being less in diameter than the opening provided in the wall therefor so that a gap is defined therebetween and filling the gap with a bushing preventing the entry and collection of material within the gap.
It is a further object of the invention to provide a mechanical seal, as aforesaid, for use in an environment wherein the bushing is adapted to protect the seal members from the damaging effects of the material attempting to enter the aforesaid gap.
It is a further object of the invention to provide a mechanical seal, as aforesaid, wherein the aforesaid bushing has a surface directly exposed to the material, which surface has a specific surface contour to assist in the repelling of the material attempting to enter the aforesaid gap.